1. Field of the Invention
The present invention relates to a boring tool for use in internal machining or the like for a prepared hole formed in a workpiece.
2. Description of the Related Art
As a tool for machining the inner periphery of a prepared hole of a rotating workpiece, for example, a boring tool is known in which a tip made of a cemented carbide alloy is detachably screwed to a front end portion of an approximately cylindrical tool body.
This boring tool is inserted in a prepared hole of a workpiece, which is supported by a main shaft of a machine tool and rotates at high speed, so as to cut the inner peripheral surface of the prepared hole with a cutting blade formed in the tip.
Since machining with the boring tool is performed in a state in which the tool body shaped like a shaft is extendedly projected, chattering is prone to arise.
For this reason, chattering has been hitherto prevented by making the tool body thick as long as it does not interfere with discharging of chips, by making the entire tool body of a high-speed steel, or by other means, in order to increase the rigidity of the tool body.
As disclosed in Japanese Unexamined Utility Model No. 4-2505, a boring tool that restricts chattering by making a tool body thicker toward the end is known to include a second chip pocket open on the outer peripheral surface of the tool body opposite from the side where a first chip pocket is open, in order to enhance chip discharging efficiency. In these cases, however, it is impossible to prevent the amplitude of chattering from increasing due to the resonance that arises when the frequency of external force (cutting resistance) applied from the workpiece to the tool and the natural frequency of a machine system including the tool coincide with each other. This is a problem in a case in which the inner peripheral surface of a deep prepared hole must be precisely finished, a case in which high dimensional accuracy is necessary, and in other cases.